Preparation and Functionalization of Cellulose Nanofibers/Polymer Composite Particles Using Various Kinds of Core Polymers

Abstract

In the present study, we investigated the development of dry powders comprising polymer particles covered with cellulose nanofibers （CNFs）. CNFs with uniform widths can prepared from wood cellulose by TEMPO （2,2,6,6-tetramethylpiperidine-1-oxyl）-mediated oxidation, which introduces carboxy groups onto the surface of the cellulose. Divinylbenzene （DVB） monomer droplets are stabilized by CNFs in an aqueous emulsion system, and it is possible to obtain poly-DVB （pDVB） microparticles that are densely covered with CNFs by polymerizing the DVB in such a system. Herein, we developed an approach to fabricating CNF-shelled composite microparticles with cores comprising various types of polymers, and investigated the properties of their carriers.We found that it was easier to stabilize the monomer droplets in an emulsion if the CNFs were modified with quaternary ammonium （QA） cations. This strategy enabled us to produce CNF-shelled composite microparticles with various types of core polymers. Moreover, the mechanical properties of these composite particles were superior to those of polymer microparticles without a CNF shell.The electronic interaction with the surface carboxy groups of the CNF shell endowed the composite particles with the pH-sensitive ability to adsorb/desorb various cationic molecules, such as antibacterial agents, metal ions, polymers, and fluorescent or redox dyes. Interestingly, when fluorescent dyes were adsorbed onto the composite particles, the emission wavelength was shorter than in the solid state, which suggests that interaction with the carboxy groups dissociated on the surfaces of the particles prevented the aggregation of the fluorescent dye.The functionalized cellulose nanofibers/polymer composite particles produced by the process have desirable mechanical and carrier properties, and are therefore potentially very useful for industrial applications and in the security field.